German Chancellor Angela Merkel said on Thursday that Europe was ready to stand by former Soviet republics in the face of possible Russian aggression.

Whether it is Moldova or Georgia, "we will show them solidarity," Merkel told the German parliament.

Like Ukraine, Moldova has come under pressure from Russia to abandon an association agreement it has negotiated with the European Union.

Russia went to war with Georgia in 2008 over the break-away territories of Abkhazia and South Ossetia.

Merkel reiterated her position that Russian intervention in the Ukrainian territory of Crimea "was a breach of international law".

Western powers have said they would not recognize the outcome of a referendum on joining Russia that Crimea will hold at the weekend.

Merkel warned Russia that it would harm itself if it failed to agree to steps to resolve the crisis in Ukraine.

"In a period of enormous uncertainty in the Ukraine, Russia has not proven to be a partner for stability for neighboring countries which it has close links to but it uses their inherent weaknesses," Merkel said. "The territorial integrity of Ukraine cannot be overridden."

"Political and diplomatic efforts are the only way out of the conflict," she added.

The Russian army continued exercises close to Ukraine's eastern borders. Some 4,000 paratroopers, 36 airplanes and 500 armored vehicles took part in drills in four regions, three of which border Ukraine, Itar-Tass news agency reported, citing defense officials.